Publications by authors named "Ohagi S"

Prohormone convertase 2 (PC2) is a member of a family of mammalian subtilisin-like endoproteases that are involved in the processing of prohormones, neuropeptides and many other precursor derived proteins. The expression of PC2 is restricted to neuroendocrine tissues such as pancreatic islets, the pituitary and the brain. To understand the regulation of the PC2 gene, we cloned and characterized the promoter region of the mouse PC2 gene.

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Insulin is synthesized in the pancreatic beta cell as a larger precursor molecule proinsulin which is converted to insulin and C-peptide by the concerted action of prohormone convertase 2 (PC2), prohormone convertase 3 (PC3) and carboxypeptidase E (CPE). One of the features of non-insulin-dependent diabetes mellitus (NIDDM) is an elevation in the proinsulin level and/or proinsulin/insulin molar ratio suggesting that mutations in these three proinsulin processing enzymes might contribute to the development of NIDDM. The identification of a mutation in the CPE gene of the fat/fat mouse which leads to marked hyperproinsulinaemia and late-onset obesity and diabetes is consistent with a possible role for mutations in CPE in the development of diabetes and obesity in humans.

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We report a sporadic case of Albright's hereditary osteodystrophy (AHO)-like syndrome with several endocrinopathies. A 37-yr-old woman had an appearance of AHO but did not have renal PTH resistance. Her case was complicated by non-insulin-dependent diabetes mellitus with severe insulin resistance, central diabetes insipidus, and hyposecretion of GH.

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A 26-year old man was admitted because of acute abdominal pain. He had received an allogeneic bone marrow transplant (BMT) for aplastic anemia 6 months before. All physical, laboratory, roentgenographic, and ultrasonographic studies were performed but nondiagnostic.

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Islet amyloid polypeptide (IAPP) was isolated from islet amyloid deposits in patients with insulinoma and pancreatic islets of non-insulin-dependent diabetes mellitus (NIDDM) and several reports suggested that it may contribute to the development of NIDDM. IAPP is mainly expressed and synthesized in pancreatic B cells and cosecreted with insulin, so analysis of the transcriptional regulation of the IAPP gene would be helpful for the elucidation of pancreatic B cell specific gene expression. The mouse IAPP gene spans about 5.

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Human obesity has an inherited component, but in contrast to rodent obesity, precise genetic defects have yet to be defined. A mutation of carboxypeptidase E (CPE), an enzyme active in the processing and sorting of prohormones, causes obesity in the fat/fat mouse. We have previously described a women with extreme childhood obesity (Fig.

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Many studies suggest that amylin, which is cosecreted with insulin from islet beta-cells, is a biologically active peptide and modulates plasma glucose levels. We therefore scanned the amylin gene for mutations in 294 Japanese NIDDM patients by single-strand conformational polymorphism, and we found a single heterozygous missense mutation (Ser-->Gly at position 20: S20G mutation) in 12 NIDDM patients (frequency 4.1%).

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Proinsulin is converted to insulin by the concerted action of two sequence-specific subtilisin-like proteases termed prohormone convertase 2 (PC2) and prohormone convertase 3 (PC3). PC3 is a type I proinsulin-processing enzyme that initiates the sequential processing of proinsulin to insulin by cleaving the proinsulin molecule on the COOH-terminal side of the dibasic peptide, Arg31-Arg32, joining the B-chain and C-peptide. Thus, PC3 plays a key role in regulating insulin biosynthesis.

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Proinsulin is converted to insulin by the concerted action of two sequence-specific subtilisin-like proteases termed prohormone convertase 2 (PC2) and prohormone convertase 3. PC2 is a type II proinsulin-processing enzyme, and it cleaves the proinsulin molecule on the COOH-terminal side of dibasic peptide, Lys64-Arg65, which joins the C-peptide and the A-chain domains. We have previously cloned and characterized the exon-intron organization of the human PC2 gene (gene symbol PCSK2), localized this gene to human chromosome 20 band p11.

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Insulin is converted from the higher molecular weight proprotein, proinsulin by highly specific proteolytic cleavage at two dibasic amino acid sites. SPC3 and SPC2, two recently identified prohormone convertase that are specifically expressed in beta cells and other neuroendocrine cells, appear to be responsible for those cleavages. We have sequenced the 5'-upstream region of the SPC3 gene and examined its promotor/enhancer activity and most of several deletion mutants in several cell lines.

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Prohormone Convertase 2 (PC2) is a specific endoprotease responsible for the processing of proinsulin to insulin. PC2 is expressed in pancreatic islets, pituitary and brain but is very low or absent in most other tissues, such as liver, spleen and kidney. To evaluate the regulated expression of the human PC2 gene we have analyzed its structure and characterized its promoter.

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We investigated the possible association between alleles of a simple tandem repeat DNA polymorphism in the human glycogen synthase gene and non-obese non-insulin-dependent diabetes (NIDDM) in Japanese subjects. Nine alleles (-4G, -3G, -2G, -1G, 0G, 1G, 2G, 3G, and 4G) were identified in the study group of 164 patients with NIDDM and 115 non-diabetic subjects. The overall frequency distribution of the glycogen synthase gene alleles was significantly different between the two groups (p = 0.

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To model islet amyloidogenesis in NIDDM and explore the glucoregulatory role of islet amyloid polypeptide (IAPP), we have created transgenic mice containing a rat insulin-I promoter-human IAPP fusion gene. Expression of human IAPP was localized to the islets of Langerhans, anterior pituitary and brain in transgenic animals; blood IAPP levels were elevated 5-fold while fasting glucose levels remained normal. Amyloid deposits have not been detected in transgenic islets suggesting that other co-existing abnormalities in NIDDM may be required for the formation of islet amyloid.

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Two restriction fragment length polymorphisms (RFLPs) near the human islet amyloid polypeptide (IAPP) gene were examined in 50 Japanese patients with non-insulin-independent diabetes mellitus (NIDDM) and 54 non-diabetic controls. RFLPs were identified with the enzymes PvuII (A1 = 21 kb and A2 = 18 kb) and BglII (B1 = 9 kb and B2 = 7 kb). These RFLPs were in complete linkage disequilibrium with A1 which was in disequilibrium with B2, as was A2 with B1.

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Experiments using recombinant vaccinia viruses expressing rat proinsulin I coinfected into COS-7 cells with recombinant vaccinia virus expressing human furin, human PC2, mouse PC3 (subtilisin-related proprotein convertases 1-3, respectively), or yeast Kex2 indicate that in this system both Kex2 and furin produce mature insulin, whereas PC2 selectively cleaves proinsulin at the C-peptide-A-chain junction. This is a property consistent with its probable identity with the rat insulinoma granule type II proinsulin processing activity as described by Davidson et al. [Davidson, H.

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In recent studies we have identified PC2 and PC3, members of a family of serine proteases that are related structurally to subtilisin, and have provided evidence that these are involved in the tissue-specific processing of prohormones and neuropeptides. PC2 is expressed at high levels in the islets of Langerhans, where it participates in the processing of proinsulin to insulin (S.P.

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We investigated the relationship between non-insulin-dependent diabetes mellitus (NIDDM) and islet amyloid polypeptide (IAPP) gene by restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR)-direct sequencing analysis. Endonuclease BglII and/or PvuII RFLP analysis revealed no positive correlation of IAPP gene with NIDDM. In PCR-direct sequencing of 25 NIDDM patients, no nucleotide sequence differences were found.

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The 37-amino acid islet amyloid polypeptide represents the major protein component present in islet amyloid deposits. Although the presence of islet amyloid is a characteristic pathological feature of the islets of humans, monkeys and cats with Type 2 (non-insulin-dependent) diabetes mellitus, it is not found in the islets of diabetic rats, mice or dogs. To further explore the molecular basis for these species differences in amyloid deposition we have used a polymerase chain reaction based method to clone cDNAs encoding the monkey (Macaca nemestrina) and dog (Canis familiaris) islet amyloid polypeptide precursors.

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Islet amyloid polypeptide (IAPP) or amylin, a recently discovered minor secretory peptide of the beta-cell related to calcitonin gene-related peptide (CGRP), is a constituent of amyloid deposits in the islets of many non-insulin-dependent (type II) diabetic individuals and some elderly nondiabetic subjects. IAPP is synthesized as a small precursor at a level of approximately 1% that of insulin and is processed, amidated, stored in beta-granules, and released along with insulin and C-peptide. Analysis of its gene (located on chromosome 12) supports an evolutionary relationship to calcitonin and CGRP, peptides with which it shares some biological actions.

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Protein tyrosine phosphatases (PTPases) are a family of enzymes that specifically dephosphorylate phosphotyrosyl residues in selected protein substrates. To more fully understand the regulatory role of protein tyrosine phosphorylation and dephosphorylation in cellular signal transduction, characterization of PTPases is essential. Using the polymerase chain reaction and degenerate oligonucleotide primers corresponding to conserved amino acid sequences within the catalytic domain of PTPases, we have identified 11 PTPase-related human liver cDNA sequences.

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